1. Field of the Invention
The present invention relates to a multi-speed automatic transmission for a motor vehicle in which the automatic transmission is arranged in a lateral direction of its vehicle body.
2. Description of the Related Art
Recently, automatic transmissions mounted on motor vehicles require more forward speed, for example more than 5-speeds, in order to improve fuel consumption, exhaust emission purification, and accelerating performance. Such a conventional multi-speed automatic transmission for a motor vehicle is disclosed in Japanese patent laid-open publication No. (Tokkaihei) 04-219553. This conventional multi-speed automatic transmission has two gear sets, one of which is a Ravigneaux type planetary gear set, or three gear sets associated with five friction elements to provide forward 6-speeds. These gear sets and friction elements are arranged in series in an axial direction of the transmission, so that it requires space longer in the axial direction for its installation on a motor vehicle, causing great difficulties in mounting it on a vehicle body, of a front-engine front-drive (FF) vehicle and a rear-engine rear-drive (RR) vehicle for example, in which the transmission is arranged in a lateral direction of the vehicle body.
In order to avoid such a disadvantage, another conventional multi-speed automatic transmission has been proposed, and disclosed in Japanese patent laid-open publication No. 2005-180665. This transmission has two planetary gear sets and five to six friction elements, the planetary gear sets and the friction elements being separated into two groups and arranged on two parallel shafts, respectively.
The above known conventional multi-speed automatic transmission, however, encounters such the following problem. Although the latter conventional automatic transmission can be shorten in its axial direction in comparison with the former conventional automatic transmission, it can not avoid arrangement of four friction elements, consisting of two clutches and two brakes, in series on an axis of one of the planetary gear set. Especially, one brake can not avoid being arranged at an outer side of a chain connecting the first and second planetary gear sets. This requires further improvement in decreasing its axial directional length in order to install the automatic transmission on a smaller vehicle.
It is, therefore, an object of the present invention to provide a multi-speed automatic transmission for a motor vehicle which overcomes the foregoing drawbacks and can decrease an axial length of the automatic transmission for easily installing it on a smaller vehicle.